The two most prevalent causes of death in Western civilization are myocardial and cerebral infarctions, conditions which are primarily the result of atherosclerotic lesions within the blood vessels supplying the heart and brain. A causal link between hypercholesterolemia due to elevated plasma concentrations of low-density lipoproteins (LDL) and very- low-density lipoprotein (VLDL) remnants and the premature development of atherosclerosis is well established. Since the majority of cholesterol transported in plasma lipoproteins is derived from hepatic biosynthesis, a prime target for drug intervention is the rate-limiting enzyme of this pathway, HMG-CoA reductase. Liver contains an AMP-activated protein kinase which is capable of almost totally inactivating HMG-CoA reductase. This kinase is regulated by the allosteric activator 5'-AMP and protein phosphorylation by a second, fatty acyl-CoA ester-activated kinase. The ultimate objective of this project is to find novel, cell-permeable, activators of these kinases for evaluation as cholesterol-lowering drugs. Phase I of the project will develop substrates, assays, and a purification scheme for the AMP-activated protein kinase. Testing of AMP analogs and purification of the second kinase will also be initiated. Phase II will develop assays which are capable of screening large chemical files and fermentations broths for activators.